It's no longer just a US $2 piece of circular plastic that unspools down a string and spools back up. A top-of-the-line yo-yo these days is a precision-engineered device with a two- or three-figure price tag. Just ask Ernest Kaiser, a.k.a. "General-Yo," an aerospace engineer working in Riverside, Calif., for a "medium-sized company that supplies big companies," as he puts it.

Last year, when out shopping for a new computer mouse, Kaiser ran across a bin of Duncan plastic yo-yos and picked one up on a whim. He hadn't played with one since he was a kid. (The yo-yo term of art, Kaiser soon learned, is throwing rather than playing.) Some number of throws and Google searches later, Kaiser discovered an entire Internet yo-yo subculture that thrives on new tricks that can be thrown only on new yo-yo designs.

Using his computer-aided design, manufacturing, and machining expertise, Kaiser created what became the first General-Yo product, the Torrent, released last December.

Built with aerospace-rated bearings, the Torrent could spin in place at the end of the string (known as "sleeping") for minutes at a time. Thanks to precision machining, it balanced well for tricks that could only be described as a kind of fast-moving, ultradynamic combination of juggling, plate spinning, and cat's cradle.

"I thought about what makes these things tick," Kaiser says. "I tried to put the weight as far out on the diameter as possible and put a very small axle on the inside, [making it] very hard to machine."

Kaiser made only 60 Torrents; they sold out in six weeks. In March, a new design, the 5-Star, sold out in one day. A second-generation 5-Star also quickly sold out.

For the holidays, Kaiser will be coming out with a new model, the Hat Trick, which will also be a limited release and undoubtedly a sellout as well.

A leading yo-yo retailer, the A2Z Science and Learning Store (http://a-two-z.com), recommends two new yo-yos that have similar specs and street cred—albeit without the aerospace-geek pedigree.

YoYoJam's New Breed, designed by national champion yo-yoer Eric Koloski, also boasts a wide body and long sleep times, which make it well suited for the catalogs of tricks chronicled on sites like Yoyoexpert.com and Yoyonation.com.

The YoYoFactory's 888 features two inner bearing-mounted wheels on either side ("hub stacks") that expert yo-yoers can grab to hold the yo-yo without stopping it from spinning.